Problem: Ashley ate 2 slices of cake. Luis ate 4 slices. If Ashley ate $\dfrac{2}{8}$ of the cake, what fraction of the cake is remaining?
If 2 slices represent $\dfrac{2}{8}$ of the cake, there must have been a total of 8 slices. $\text{fraction of cake remaining} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 6 slices, which leaves 2 out of 8 slices remaining. There is $\dfrac{2}{8}$ of the cake remaining.